CE Compliance and Beyond

CE stands for “Conformite Europeenne” or European Conformity. CE Compliance means that the product meets all of the applicable European Union (EU) Directives. These requirements govern the compliance of devices sold on the European market. There are various CE regulations and some are mandatory only when the device is placed in a specific environment. For transducers, CE compliance always requires electromagnetic compatibility or EMC testing.

Electromagnetic Interference (EMI) is electrical energy in the wrong place at the wrong time. This unwanted electrical energy is present everywhere and can cause unintended and unpredictable responses in electronic equipment. Electronic devices have the potential to be a source of, or receptor for, this unwanted interference or “noise”.

Walkie-Talkies, which are used extensively

within industrial manufacturing and processing

environments, are an example of devices that can

create excessive amounts of EMI. They generate

powerful signals that can cause false readings

on nearby instrumentation. Pressure transducers

are extremely susceptible to the effects of this

interference. Their circuitry amplifies the low-level

sensor signal along with any unwanted noise.

There are many other sources of EMI, including cell

phones, wireless transmitters, motors, generators,

power line disturbances, and lighting, to name a few.

To better understand and minimize the effects

of electromagnetic interference, instrument

manufacturers perform EMI testing, which mimics

the environment a piece of equipment would be

placed in. This testing confirms the electromagnetic

compatibility (EMC) of a device (i.e. the ability to

perform its intended function in an environment

where EMI is present).

CE EMC Requirements

Testing of an electronic device in the simulated environment allows

for the development of a more reliable and robust product. Various

standards and regulations exist throughout the world. Some of these

regulations are voluntary and some require mandatory compliance.

The testing required to meet the CE EMC standard depends on

the type of device being tested and its intended environment.

According to the EN 61326 standard, transducers used for the

measurement of pressure must undergo specific tests to ascertain

their immunity to noise typically encountered by this category of

electronics. Depending on their circuitry, it may also be necessary

to test emissions to confirm their environmental compatibility.

EMC Immunity testing may include:

■ Radiated Immunity (from EMI generated by nearby

devices and equipment)

■ Conducted Immunity (to disturbances on power lines)

■ Surges (transient high voltage which could be caused by

nearby lightning and other phenomena)

■ Bursts (fast, repetitive, low-energy electrical transients that

could be caused by the cycling of relays and other equipment)

■ Electrostatic Discharges (ESD)

With all of these tests, except for surge, the standard limits

the allowable deviation. This limit is based on the accuracy the

manufacturer specifies on the product. Surges are a special case.

There is no deviation limit specified for a device during the surge test.

The device passes the test if it returns to a valid output.

CE EMC Testing

Some companies send their designs to third party

certification laboratories for testing and receive

pass/fail reports. Viatran typically takes the new

designs to a third party facility for EMC testing. A

Viatran design engineer takes the new design along

with a broad array of resistors, capacitors and tools.

This way they can make CE compliance circuitry

modifications and test them on the spot.

The facility has the required test equipment to

perform the EMC tests. This includes an anechoic

chamber. The chamber is used during radiated

immunity testing to minimizes external sources of

EMI. During radiated immunity testing, the pressure

transducer is set up in the chamber and monitored

by test equipment that is outside the anechoic

chamber. The transducers are subjected to EMI at

various frequencies and multiple directions while the

results are recorded and monitored.

Transducers may be very sensitive to EMI at some

frequencies and not very sensitive at others. For

radiated immunity testing, frequencies from

80MHz to 2.7GHz are scanned. During this test,

the unit is monitored to expose those frequencies

the transducer is most susceptible to. Circuit

modifications can be made to optimize circuit

performance. When these changes are completed,

Viatran will scan through the entire range one

more time to make sure the response is good at

all frequencies.

Photograph courtesy of Parker-Chomerics Test Services.

Photograph courtesy of Parker-Chomerics Test Services.

Based on numerous hours spent at the test facility, Viatran knows

how to design circuits that minimize the effects of the EMI.

For example, printed circuit board layout is critical. Circuitry designed

to filter out EMI should be placed as close to the connector as possible.

Design engineers are careful to create as much distance as possible

between CE EMC filtering circuitry and sensitive sensor signal

conditioning circuitry within the transducer. In addition, sensitive

circuitry is shielded from this filtering circuitry by a ground plane.

Viatran will sometimes take in several units with different

configurations, compare their performance and determine the

most noise hardened design. In addition, to ensure a superior

product, Viatran may test transducers beyond the required CE

EMC specifications. Viatran has learned a lot over the years and

accumulated a knowledge base that is very helpful.

Even Better EMI Attenuation

Most of Viatran’s transducer designs and all of those introduced since

2006 are CE EMC certified. This provides a high level of confidence

that these pressure sensors will perform as specified in environments

where EMI is a concern.

An example of such an environment is deep well oil drilling where

pressure readings are used for directional control of drill bits

thousands of feet below the surface. These signals are often very

weak and could easily be degraded by the many electrical motors

and Walkie Talkies present at an oil drilling site. In cases like these,

users can specify EMC to even higher standards than those required

for CE. These specifications can be met by using specially designed

transducers or modifying existing models to incorporate additional

EMI filtering.

These users should pay careful attention to make

sure the transducer is installed with a good, solid

case ground. As a rule of thumb, shielded cables

should be grounded at either the data acquisition

end or transducer end of the cable to avoid the

possibility of creating ground loops. The optimal

grounding configuration depends on a variety

of factors present within the environment and

application installation.

It helps to understand the typical sources of EMI

in a particular application environment. It may

be possible to minimize the effects of these EMI

generators by modifying the equipment or locating

it away from critical pressure sensors.

The application specialists at Viatran have years

of field and laboratory experience with transducers

used in EMI environments. They should be

approached early on for advice.

Viatran

199 Fire Tower DriveTonawanda, NY 14150 USA

International: 1-716-629-3800Toll Free: 1-800-688-0030Fax: 1-716-693-9162Email: solutions@viatran.comWeb: www.viatran.com